This invention generally relates to vascular catheters and particularly low-profile steerable catheters for angioplasty procedures, such as percutaneous transluminal coronary angioplasty (PTCA).
In PTCA procedures, a dilatation catheter having an inflated balloon on the distal end thereof is advanced through a patient's arterial system until the deflated balloon crosses the atherosclerotic lesion to be dilated. The balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures to compress the atherosclerotic plaque against the inside of the artery wall and then the balloon is deflated so that the catheter can be removed and blood flow resumed.
Typically, a guiding catheter having a preformed distal end is first percutaneously introduced into the patient's arterial system with the distal tip in the coronary artery. A guidewire is advanced through the guiding catheter into the patient's coronary anatomy until the distal end of the guidewire crosses the lesion to be dilated. The dilatation catheter is then advanced over the guidewire, with the guidewire slidably disposed within an inner lumen of the catheter, until the inflatable balloon is positioned within the lesion. For a more detailed description of angioplasty procedures and the devices used in such procedures, reference is made to U.S. Pat. No. 4,332,254 (Lundquist); U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.) U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.); and U.S. Pat. No. 4,616,652 (Simpson) which are hereby incorporated herein in their entirety.
Steerable dilatation catheters with built-in guidewires or guiding elements are being used with greater frequency because the deflated profile of such catheters are generally smaller than conventional dilatation catheters having the same inflated balloon size. Further details of low-profile steerable dilatation catheters may be found in U.S. Pat. No. 4,582,181 (Samson) which is hereby incorporated in its entirety by reference thereto. The lower profile of these catheters allows the catheter to cross tighter lesions and to be advanced much deeper into the patient's coronary anatomy. Moreover, the use of steerable low-profile dilatation catheters having a built-in guidewire or guiding element shortens considerably the time for the angioplasty procedures because there is no need to first insert a guidewire and then insert a conventional dilatation catheter over the previously inserted guidewire.
However, it has been found that the balloon elements of commercially available very low-profile steerable catheters tend to wrap on themselves when the catheter is torqued so that the balloon frequently will not completely inflate when positioned across a stenosis or if inflated to deflate within a desired time period. Some suppliers of such catheters recommend that the catheter be limited to one rotation to avoid such balloon wrapping. However, such restrictions on rotations severely limit the steerability of the catheter within a patient's vasculature.
What has been needed and heretofore unavailable is a steerable dilatation catheter having a very low profile which can be torqued from the proximal end thereof without wrapping the inflatable balloon element. The present invention satisfies this and other needs.